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Leptaenella ventricosa
Taxonomy
Strophomena depressa ventricosa was named by Hall (1857). Its type specimen is BB.29044-45, a valve (Incomplete external and internal mould of brachial valve), and it is a 3D body fossil. It is the type subspecies of Leptaenella.
It was recombined as Strophomena rugosa ventricosa by Hall (1859); it was recombined as Leptaena rhomboidalis ventricosa by Hall and Clarke (1892); it was recombined as Leptaenella ventricosa by Fredericks (1918); it was recombined as Leptaena ventricosa by Stewart (1922) and Amsden and Ventress (1963).
It was recombined as Strophomena rugosa ventricosa by Hall (1859); it was recombined as Leptaena rhomboidalis ventricosa by Hall and Clarke (1892); it was recombined as Leptaenella ventricosa by Fredericks (1918); it was recombined as Leptaena ventricosa by Stewart (1922) and Amsden and Ventress (1963).
Synonymy list
| Year | Name and author |
|---|---|
| 1857 | Strophomena depressa ventricosa Hall pp. 55-56 |
| 1859 | Strophomena rugosa ventricosa Hall pp. 417-418 figs. pl. 94, figs. 2a,f, 3 |
| 1892 | Leptaena rhomboidalis ventricosa Hall and Clarke figs. pl. 15a |
| 1918 | Leptaenella ventricosa Fredericks p. 89 |
| 1922 | Leptaena ventricosa Stewart p. 231 figs. pl. 61 f. 15-17 |
| 1963 | Leptaena ventricosa Amsden and Ventress pp. 76 - 78 figs. Plate 2, figures 9-14 |
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If no rank is listed, the taxon is considered an unranked clade in modern classifications. Ranks may be repeated or presented in the wrong order because authors working on different parts of the classification may disagree about how to rank taxa.
†Leptaenella ventricosa Hall 1857
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Diagnosis
| Reference | Diagnosis | |
|---|---|---|
| Stewart 1922 | Concavo-convex, strongly geniculate Leptaena with disc surrounded by prominent fold with wavelength of 2-3 mm., disc transversely quadrate, about 9 mm. long, just over three-fifths as long as wide and with ventral depth of about one-fifth the length due to strongly convex ventral umbo, trail bent back sharply at about 90 to give an overall depth of about one-half the length of pedicle valve ; radial ornamentation parvicostellate and not well differentiated into segments, commonly with 4 rounded costellae per mm., 10 mm. antero-medianly of ventral umbo ; 8 or 9 concentric and rarely discontinuous rugae, with wavelength less than 1 mm., in later formed ones also ornament disc ; pseudodeltidium small, foramen small, commonly sealed in adult shells, chilidium large, convex and commonly bearing slight median depression ; teeth large, strongly striated, obliquely splayed and fused with widely divergent short dental lamellae, ventral muscle scar elongately rhomboidal in outline, nearly nine-tenths as wide as long and extending anteriorly for nearly three-quarters the length of disc in adult shells, adductor scars small, lanceolate, separated posteriorly by low median ridge extending from low median platform occupying delthyrial floor, submedian diductor lobes extending well beyond adductors but not enclosing them ; cardinal process lobes well developed, high and separated by faint median ridge, sockets striated, notothyrial platform anchor-shaped with short median stem and strongly curved lateral ridges fused with socket ridges and enclosing posteriorly the subcircular adductor impressions ; a pair of curved submedian ridges originate near median prolongation of notothyrial platform to divide adductor impressions and converge anteriorly commonly to contain anterior median ridge. | |
| T. W. Amsden and W. P. S. Ventress 1963 | All reasonably complete shells show a well-marked, rugose visceral disc separated from the non-rugose trail by a sharp geniculation; however, the disc exhibits considerable variation, being almost flat on some individuals (pl. II, fig. 10) and strongly concave on others (pl. II, figs. 12, 13). On some specimens (pl. II, fig. 13 ) the trail -is large, equaling or even exceeding the length of the visceral disc. (This structure is broken on many shel1s, so that it is impossible to determine the original size.) Although the outline varies considerably, most shells are transversely subquadrate, the length/width ratio falling between 0.6 and 0.8, but on a couple of specimens the length and width are nearly equal. Our collections include only a few fragmentary brachial valves. |